1. Field of the Invention
The present invention relates to equipment for pipe string such as drill pipe string comprising a side entry connection for passing a cable from the inside to the outside of the pipes, with hydraulic sealing about the cable.
2. Description of the Prior Art
Side entry connections (generally designated by side entry subs in the oil industry) are well known by oil drilling specialists. Such a device is for example described in the British Pat. No. 2,135,719.
A side entry connection is, for example, used in the technique described in the French Pat. No. 2,501,777 (EN 81/05.271) and its first two additions EN 82/03.317 and EN 84/08.369.
According to this technique, for carrying out well-logging or interventions in horizontal or steeply inclined wells, a logging probe or an intervention tool is initially fixed to the lower part of a pipe string which is lowered into the well as it is formed.
Then an electric cable is lowered inside the pipes (by gravity and by pumping) having a weighted connector (the connector has mounted thereover a load bar) which is connectable to a complementary connector fixed to the top of the probe (or the tool). In the portion of the pipe string corresponding to the vertical or slightly inclined part of the well, a side entry connection allows the cable to pass from the inside to the outside of the pipes.
Recording of the measurement (or the intervention in the well) is effected by moving the pipe string assembly from the surface.
Present equipment comprising a side entry connection raise a problem, however, should the pipe string be jammed in the well.
In fact, the presence of the electric cable contained inside the rods in the part between the side entry connection and the load bar does not allow operations to be carried out for unjamming the pipe string.
These unjamming operations or interventions are, for example, the introduction into the pipe, from the surface, of specialised tools which have to be lowered by means of a cable as far as the zone (which is generally situated under the side entry connection) which comprises the pipes jammed by the formation.
These specialized tools may, for example, be an explosive for unscrewing the jammed pipe.
Moreoever, the presence of the cable inside the pipe string, above the side entry connection, limits the possibilities of rotation of the pipe string.